We are all shaped by our experiences as engineers. Our early experiences as young engineers are especially influential. 

I first worked in the aerospace industry for five years and then the nuclear industry for two years. At each of these companies we relied heavily on a handbook written originally in Russian by a Russian engineer. I am talking about the Handbook of Hydraulic Resistance by I.E. Idelchik. This book is my "go to" book on any unusual pipe system configuration hydraulic calculations and, especially, with calculations at tees and wyes.

In that we used Idelchik at both of my first two jobs, when I started AFT in 1993 I assumed that everyone knew about and used Idelchik. I found out that was not the case. If you have not heard of Idelchik's handbook, it is voluminous at 861 pages. It has by far the best information available on how to calculate pressure losses in tees and wyes. And it has tons of references. All in Russian. It has been translated into English, French, Chinese and Czech.

My first experience in aerospace was with the 1st English edition translated in 1966. My next experience in nuclear was with the 2nd English edition which was published in 1986. 

Using Idelchik is tricky. First, the nomenclature follows a different tradition than English speaking engineering. For example, the loss factor "K" is referred to as "ζ". Second, there are many, many equations and charts and symbols and subscripts. The English translations have always been rife with typos on the symbols and subscripts. You have to pay close attention to the development of the data to have any chance to catch the typos. And cross-check constantly.

At my second job working for Babcock & Wilcox on nuclear related systems in 1992-1993 we had a highly marked up copy of the 2nd Edition with hundreds of typos identified. We heard the publisher was working on a 3rd Edition. As a service to the engineering community we made an exhaustive list of all the typos so they could be corrected in the 3rd Edition. We sent these to the publisher. Unfortunately, our list of corrections was not implemented when the 3rd Edition came out in 1994.

At AFT we have used the 3rd Edition in our software since AFT Fathom 2, AFT Arrow 1 and AFT Impulse 1 - all released in the mid-1990's. We are aware of how the nuclear industry relies on Idelchik's handbook because of how often they ask about it and use Idelchik features in our software. There are some customers in the nuclear industry who have decided to buy AFT software almost entirely based on the fact that we have Idelchik data included - especially for tees.

Today the world is a crazy place with much tension between Russia and the USA. It is heartening to see what Idelchik wrote in the Preface to the 1st English Edition:

The author hopes that the present edition will not only be useful for the further development of engineering science and technology in the English-speaking countries but will also aid in fostering friendly relations between the peoples of these countries and the Soviet people.